Bacteria of the species Bacillus sphaericus deposit a high molecular weight protein on the outer surface of the cell. In some strains this protein displays a regular array of subunits (RS or T layer), but in other strains the protein layer is non-regularly structured (NRS layer). The latter situation is true for all of the strains which are pathogenic for mosquito larvae. Some of these pathogenic strains which produce a potent and very specific toxin against mosquito larvae are being considered for development as larvicides. They may provide a useful new tool for the control of vector borne diseases. The overall goal of this project is to examine some of the properties of the high molecular weight NRS protein on the cell surface of a number of mosquito pathogenic strains of B. sphaericus. This will be done by comparing melecular weights of the proteins by electrophoresis, their isoelectric points by isoelectric focusing, and their composition by peptide mapping. The NRS proteins will also be compared to RS proteins from other selected strains. The role of the proteins as bacteriophage adsorption sites will be investigated. A hypothesis is to be tested is that the NRS proteins are the adsorption sites for 10 bacteriophages used in a phage typing scheme and that the surface proteins will be biochemically and or immunologically distinguishable among the phage groups. The specificity of adherence that exists between the NRS protein and the underlying peptidoglycan sacculus will also be determined. This project is part of the long range plan to obtain a better understanding of structure-function relationships in these bacteria. The surface proteins may be important in determining the survival and/or growth of these bacteria in insect larvae which consume them. The proteins may also be important in practical aspects of formulating the bacteria into larvicides.